Need help with fuel tank problem

[pbierre]

Pbierre, Here's a link with a good write up and photos. Shows EVAP components and more importantly how to access them for repairs.

https://www.matthewsvolvosite.com/fo...ic.php?t=64017

Scot850 did a terrific job with this repair writeup. Thanks, FV.

[hoonk]

We're talking about the filler vent hose fitting, right? It's at about the 60% fill height of the tank. If tank bib seal were leaky, we should see liquid fuel oozing out plus raw gas smell. I have to fill above 7/8 level to get any raw gas fumes, leading me to believe the leak is something connected up high. Roll-over valve, tank pressure sensor??? Smoke test next week.

No the crack in my 01 was at a different fitting (~same size hose) near the top of the tank in the center, it only leaked/smelled when the car was filled up

[pbierre]

The saga continues. I tore out the rear seats (disconnected battery first). Warning: With rear seats unplugged from the computer, you'll get a "Urgent SRS problem" warning. I removed the 2 access hole covers (fuel pump and fuel level sender), to get a slim view of the fuel tank top surface.

Then I took it to an indie shop for a smoke test. He ran the smoke test with the car up on the lift. He noticed a smoke leak coming from top of fuel tank, on passenger side.

"Leakage measured 0.026 inches of water"

The shop didn't have an endoscope, and didn't bother to inspect smoke leak from top-side access holes.

Next step: I'll take off the fuel tank support straps, and lower the tank onto the propeller shaft. It should drop about 1". That will give me 2" of clearance from the access portals on the top-side to reach in with a cellphone camera, or go in with endoscope I can borrow from the library. There should be fuel gunk trail pinpointing where the vapor leak is. Will wait until tank is almost empty to drop it down.

[pbierre]

Smoke test done. I went into the smoke test with 3/4 tank of gas. Should've gone in with <1/8 tank.

That said, the leak was proven during the test to be a hairline crack in the weld where the blue plastic hose bib (filler vent hose) is plastic-welded to the tank body.
Smoke didn't come out, but liquid gasoline was oozing out as the tank level was above the leak point. The pressure during the test caused gas to ooze-- under normal driving, the tank is vented, not under any pressure.

I bought a tank repair epoxy kit.

The "SRS Urgent Repair Needed" DTC was thrown after starting the car up with the rear seats removed (unplugged from the system). Will have to have dealer reset this code -- these SRS system faults are not something I can reset with iCarSoft OBD-II scanner.

[pbierre]

FINAL RESOLUTION:

No less than 3 Volvo shops advised me that the fuel tank would have to be replaced, estimates around $3200 (the Haldex and propeller shaft have to be removed, as well as the rear seats, fuel pump and level sender).
The new tank assy. part was quoted at $1400.

I was able to fix the leak using plastic welding.

I went to the junkyard, and sawed out a 6"x 6" (150 x 150 mm) piece of fuel tank from the same MY, thus assuring plastics compatibility.

Since the leak was along a circular joint around the filler vent hose bib, I cut a donut shaped patch out of the scrap material. I used a 2" (49mm) dia. hole saw to cut a circular disk, then used a 13/16" (21mm) dia. boring bit to cut out the donut hole. I judged the patch to be too thick to melt, so in a vise I sawed it into two donuts half as thick, and only used one. The patch was about 2mm thick.

The car's rear end was jacked up about 6", and the pass. side wheel removed. This is so that I could address the repair from both the side and underneath.

At Harbor Freight, I bought the Chicago Electric 80W plastic welding iron ($16). The tip is just the right size, but I advise getting some practice with scrap material. It's low enough power, there is little risk of burning through the tank (1/4" thick fiberglass-reinforced high-density polyethylene).

The hose must be removed from the bib to get the donut patch on. I used a Dremel cutter to release the factory crimp-style hose clamp. It's safer to do the welding with the hose put back on the bib (closing off gasoline fumes).

The welding was a bit messy. The hose bib was likely a different kind of plastic as the tank, and didn't blend as easily into the weld.

That said, the Check Engine Light faults have stopped (with tank between 15-85% full), and so the plastic weld did the trick.

(I'll have to pay the Volvo dealer $95 to clear the SRS "urgent service needed" code. I drove the car with the rear seats removed to the shop to get a smoke-pressure test - you have to pin down a hairline leak this way. Only the Dealer-enabled VIDA can reset SRS faults, and it leaves a record attached to the VIN at Volvo Corp.
Something to think about before removing the seat(s)).

Visual inspection for gunk trail:


Location on fuel tank:


Scavenged fuel tank scrap, annular patches, and plastic welding kit:


Pre-welding view:

[pbierre]

The saga continues. I tore out the rear seats (disconnected battery first). Warning: With rear seats unplugged from the computer, you'll get a "Urgent SRS problem" warning. I removed the 2 access hole covers (fuel pump and fuel level sender), to get a slim view of the fuel tank top surface.

Then I took it to an indie shop for a smoke test. He ran the smoke test with the car up on the lift. He noticed a smoke leak coming from top of fuel tank, on passenger side.

"Leakage measured 0.026 inches of water"

The shop didn't have an endoscope, and didn't bother to inspect smoke leak from top-side access holes.

Next step: I'll take off the fuel tank support straps, and lower the tank onto the propeller shaft. It should drop about 1". That will give me 2" of clearance from the access portals on the top-side to reach in with a cellphone camera, or go in with endoscope I can borrow from the library. There should be fuel gunk trail pinpointing where the vapor leak is. Will wait until tank is almost empty to drop it down.

I was unsatisfied with the first smoke test. "Somewhere on the top of the tank" was too vague to be actionable. So I took it back for a restest at their expense,
and was shown the exact leak point -- a hairline crack in the plastic weld between the tank and the filler vent hose bib). It's on the rear side of the tank, on the passenger side, near the top.

[pbierre]

This complex repair is now completed, going to the Volvo dealer to have their VIDA clear the "SRS - Airbag Urgent Service" (a result of my removing the rear seatbacks).

The next 2 posts detail how a smoke test was used to locate the tank leak, and how plastic welding succeeded in patching it.